Exposure to highly toxic materials, and especially chemical warfare agents, is a potential hazard to both the armed forces and civilian populations. Such chemical warfare agents possess toxic properties capable of killing, injuring or incapacitating people. It has been estimated that about 25 to 27 nations currently possess chemical weapons, often referred to as the “poor man's nuclear weapon.” The manufacture of chemical warfare agents in small quantities by terrorists is an ongoing threat, and the manufacture and use of military quantities of chemical warfare agents for delivery against U.S. troops is always a real potential.
Some commonly known chemical warfare agents are bis-(2-chloroethyl) sulfide (HD or mustard gas), pinacolyl methylphosphonofluoridate (GD) and O-ethyl S-(2-diisopropylamino)ethyl methylphosphonothioate (VX), as well as analogs and derivatives of these agents. These chemical warfare agents are generally delivered as fine aerosol mists which, aside from presenting an inhalation threat, will deposit on surfaces of military equipment and hardware, including uniforms, weapons, vehicles, vans and shelters. Once such equipment and hardware is contaminated with one of the previously mentioned highly toxic materials, the agent must be removed in order to minimize contact hazards.
For this reason, there is a crucial need to develop and improve technology for decontamination of highly toxic materials. This is especially true for the class of toxic agents known as nerve agents or nerve gases which are produced and stockpiled for both industrial use and as chemical warfare agents. Simply by way of example, one class of nerve agents with a high level of potential lethality is the class that includes organophosphorus-based (“OP”) compounds, such as Sarin, Soman, and VX. Such agents can be absorbed through inhalation and/or through the skin of an animal or person. The organophosphorus-type (“OP”) CW materials typically manifest their lethal effects against animals and people by inhibiting acetylcholine esterase (“AChE”) enzyme at neuromuscular junctions between nerve endings and muscle tissue to produce an excessive buildup of the neurotransmitter acetylcholine, in an animal or person. This can result in paralysis and death in a short time.
In addition to the concerns about chemical warfare agents, there is also a growing need in industry for decontamination of industrial chemicals and/or insecticides, for example, ACHE-inhibiting pesticides such as parathion, paraoxon and malathion, among others. Thus, it is very important to be able to effectively detoxify a broad spectrum of toxic agents, including, but not limited to, organophosphorus-type compounds, from contaminated surfaces and sensitive equipment.
Chemical warfare agents and related toxins are so hazardous that simulants have been developed for purposes of screening decontamination and control methods.
These simulants are 2-chloroethylphenyl sulfide (CEPS), an HD simulant, dimethyl methyl phosphonate (DMMP), a G-agent simulant, and O,S-diethylphenylphosphonothioate (DPPT), a VX simulant.
The U.S. Army uses a decontamination material called XE555 resin (Ambergard™ Rohm & Haas Company, Philadelphia, Pa.). XE555 is presently being used by the military for immediate decontamination applications. The objective of immediate decontamination operations is to remove toxic agents from the contaminated surface as rapidly as possible. However, XE555 has several disadvantages. Although effective at removing chemical agents, XE555 does not possesses sufficient reactive properties to neutralize the toxic agent(s) picked up by this resin. Thus, after use for decontamination purposes, XE555 itself presents an ongoing threat from off-gassing toxins and/or vapors mixed with the resin. In addition, XE555 is relatively expensive in the quantities required for decontamination purposes.
Recently, reactive sorbents have been developed and used to both absorb and react with highly toxic materials to yield less toxic products. For example, the U.S. Army uses M100 sorbent decontamination system (SDS) for decontamination of highly toxic materials. The M100 SDS utilizes an alumina-based reactive sorbent called A-200-SiC-1005S, which is in the form of a powder. The reactive sorbent powder acts as an inexpensive, non-corrosive, non-harmful absorber designed to be rubbed onto a contaminated surface and does not require water rinse or special disposal. The reactive sorbent is structured to flow readily across a contaminated surface, and is highly porous, allowing it to absorb the highly toxic material quickly. The absorbed highly toxic material is strongly retained within the pores of the sorbent, which reacts to form less toxic products, thereby minimizing off-gassing and contact hazards.
Bartram and Wagner (U.S. Pat. No. 5,689,038, incorporated by reference herein) report the use of an aluminum oxide and a mixture of aluminum oxide and magnesium monoperoxyphthalate (MMPP) as reactive sorbents to decontaminate surfaces contacted with droplets of chemical warfare agents. It has been reported that both materials were able to effectively remove such toxic agents from a surface to the same extent as XE555. In addition, both materials represented improvements in chemical warfare agent degrading reactivity and in reducing off-gassing of toxins relative to XE555. The reported sorbents were based on pre-existing, commercially available materials, such as Selexsorb CD™, a product of the Alcoa Company. Essentially, Bartram and Wagner reported that their aluminum oxide is modified by size reduction, grinding or milling.
Bartram and Wagner (U.S. Pat. No. 6,537,382, incorporated by reference herein) report the use of two types of reactive sorbents. One comprises metal exchanged zeolites such as silver-exchanged zeolite, and the other comprises sodium zeolites. The reactive sorbents are disclosed to remove chemical agents from the surface being decontaminated, and then begin decomposing the absorbed chemical agents. Similar in all reactive sorbents, this dual action provides the advantage of reducing the risks associated with potential outgassing from the sorbent, and reducing the toxicity of the sorbent for disposal purposes.
Although, current forms of reactive sorbents as solid—phase decontaminants are capable of absorbing and removing highly toxic materials including chemical warfare agents from surfaces, their capacity to react with the highly toxic materials is limited and prolonged as compared to liquid-phase decontaminants. Thus, for a time after application, the contaminated reactive sorbents present a persistent hazard as the highly toxic materials slowly react and decompose in the sorbents.
Applicant has theorized that the primary reason why reactive sorbents react slowly with highly toxic materials including chemical warfare agents is the slow diffusion of the materials once they are absorbed. The absorbed materials in the form of droplets are concentrated within the pores of the reactive sorbent, and depending on volatility, typically spread across the surface at a slow rate. It is therefore believed that the slow diffusion of the highly toxic materials within the reactive sorbent results in low reactivity. To enhance diffusion, solvents may be employed to spread and more uniformly distribute the highly toxic materials across the surface of the reactive sorbent. This results in a slurry mixture that exhibits enhanced reaction rates relative to the dry powder reactive sorbent. However, the production and handling of a slurry mixture on-site greatly complicates the decontamination process and hinders clean up afterward.
Thus, there remains a need in the art for even more effective, chemically modified forms of reactive sorbents, and for still further compositions and methods, optimized to allow for the rapid and effective removal and/or decontamination of chemical warfare agents and related highly toxic materials in an environmentally acceptable and cost-effective process.